The specific aim of this research program involves studies on chemical and biological nature of human chorionic gonadotropin-like substances in tissue and biological fluids from normal subjects with particular emphasis on the isolation, purification and characterization. Generation of specific antibodies based on the unique chemical structure of human chorionic gonadotropin and through chemical modification of the structure has been undertaken. BIBLIOGRAPHIC REFERENCES: Chen, H.C., Ayala, A.R., Hodgen, G.C., Birken, S., Canfield, R.E. and Ross, G.T.: First Specific Assay for Chorionic Gonadotropin in Human Urinary Extracts. Clinical Research 24: 375A, 1976. Schreiber, J.R., Rebar, R.T., Chen, H.C., Hodgen, G.D., and Ross, G.T.: Limitation of the Specific Serum Radioimmunoassay for Human Chorionic Gonadotropin in the Management of Trophoblastic Neoplasms. Am. J. Obstet. 125: 705-707, 1976.